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Yago T. Analytical model for spin dynamics in radical pairs under the spin-locking condition. J Chem Phys 2024; 160:244701. [PMID: 38912632 DOI: 10.1063/5.0210982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 06/04/2024] [Indexed: 06/25/2024] Open
Abstract
Spin dynamics in triplet radical pairs are theoretically studied under the spin-locking condition, where singlet-triplet mixing is blocked by the resonant microwave field. A key assumption in the theory is simultaneous excitations of T+-T0 and T--T0 transitions in triplet radical pairs. This assumption allows for the application of a three-state model [Yago, J. Chem. Phys. 151, 214501 (2019)] to describe the spin dynamics of triplet radical pairs. The analysis based on the three-state model shows that the triplet states are quantized along the direction of a microwave-induced magnetic field (B1) in the rotating frame under the spin-locking condition. This gives rise to a new spin-locking phenomenon where T+-T0 and T--T0 mixing are most enhanced at magnetic fields that deviate from the resonance by ±B1. It is also shown that the quantum beats observed under the spin-locking condition originate from the spin dynamics in triplet radical pairs.
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Affiliation(s)
- T Yago
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama 338-8570, Japan
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2
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Li Y, Zhang Z, Li T, Liang Y, Si W, Lin Y. Highly-Active Chiral Organic Photovoltaic Catalysts with Suppressed Charge Recombination. Angew Chem Int Ed Engl 2023; 62:e202307466. [PMID: 37403233 DOI: 10.1002/anie.202307466] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 07/03/2023] [Accepted: 07/04/2023] [Indexed: 07/06/2023]
Abstract
Recombination of free charges in organic semiconductors reduces the available photo-induced charge-carriers and restricts photovoltaic efficiency. In this work, the chiral organic semiconductors (Y6-R and Y6-S with enantiopure R- and S- chiral alkyl sidechains) are designed and synthesized, which show effective aggregation-induced chirality through mainchain packing with chiral conformations in non-centrosymmetric space groups with tilt chirality. Based on the analysis of spin-injection, magnetic-hysteresis loop, and thermodynamics and dynamics of the excited state, we suggest that the aggregation-induced chirality can generate spin-polarization, which suppresses charge recombination and offers more available charge-carriers within Y6-R and Y6-S relative to the achiral counterpart (Y6). Then the chiral Y6-R and Y6-S show enhanced catalytic activity with optimal average hydrogen evolution rates of 205 and 217 mmol h-1 g-1 , respectively, 60-70 % higher than Y6, when they are employed as nanoparticle photocatalysts in photocatalytic hydrogen evolution under simulated solar light, AM1.5G, 100 mW cm-2 .
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Affiliation(s)
- Yawen Li
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhenzhen Zhang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tengfei Li
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yuanxin Liang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wenqin Si
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuze Lin
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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Nikiforov D, Ehrenfreund E. Magnetic Field Effects of Charge Transfer Excitons in Organic Semiconductor Devices. Isr J Chem 2021. [DOI: 10.1002/ijch.202100091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Daniel Nikiforov
- Physics Department and Solid State Institute Technion-Israel Institute of Technology Haifa 3200003 Israel
| | - Eitan Ehrenfreund
- Physics Department and Solid State Institute Technion-Israel Institute of Technology Haifa 3200003 Israel
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Nikiforov D, Khachatryan B, Tessler N, Ehrenfreund E. Effects of fast back-fusion of charge transfer excimers on magneto-photocurrent in organic light emitting diodes. J Chem Phys 2020; 152:034707. [PMID: 31968974 DOI: 10.1063/1.5131481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We report the magnetic field dependence of the magneto-photocurrent (MPC) in organic light emitting diodes made of homo-polymer organic layers and compare it to the measured magneto-conductance (MC) in the same diodes. We find that the response MPC(B) is very different from MC(B) in at least two respects. (a) The low field (B < 50 mT) response of MPC(B) is narrower by a factor of ∼5 from that of MC(B). (b) At high fields (B > 4 T), MPC(B) has a stronger dependence on B, d(MPC)/dB ∼ 5d(MC)/dB. We attribute these differences to a unique feature of charge transfer excimers that are responsible for MPC: sub-ns fast fusion back to singlet excitons and slow (ns to μs) dissociation to free charges. In contrast, MC(B) is determined by long lived (>10 ns) polaron pairs having singlet and triplet dissociation rates of the same order.
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Affiliation(s)
- D Nikiforov
- Physics Department, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - B Khachatryan
- Physics Department, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - N Tessler
- Department of Electrical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - E Ehrenfreund
- Physics Department, Technion-Israel Institute of Technology, Haifa 32000, Israel
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Grünbaum T, Milster S, Kraus H, Ratzke W, Kurrmann S, Zeller V, Bange S, Boehme C, Lupton JM. OLEDs as models for bird magnetoception: detecting electron spin resonance in geomagnetic fields. Faraday Discuss 2019; 221:92-109. [PMID: 31553007 DOI: 10.1039/c9fd00047j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Certain species of living creatures are known to orientate themselves in the geomagnetic field. Given the small magnitude of approximately 48 μT, the underlying quantum mechanical phenomena are expected to exhibit coherence times in the microsecond regime. In this contribution, we show the sensitivity of organic light-emitting diodes (OLEDs) to magnetic fields far below Earth's magnetic field, suggesting that coherence times of the spins of charge-carrier pairs in these devices can be similarly long. By electron paramagnetic resonance (EPR) experiments, a lower bound for the coherence time can be assessed directly. Moreover, this technique offers the possibility to determine the distribution of hyperfine fields within the organic semiconductor layer. We extend this technique to a material system exhibiting both fluorescence and phosphorescence, demonstrating stable anticorrelation between optically detected magnetic resonance (ODMR) spectra in the singlet (fluorescence) and triplet (phosphorescence) channels. The experiments demonstrate the extreme sensitivity of OLEDs to both static as well as dynamic magnetic fields and suggest that coherent spin precession processes of coulombically bound electron-spin pairs may play a crucial role in the magnetoreceptive ability of living creatures.
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Affiliation(s)
- Tobias Grünbaum
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
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Chiodi F, Bayliss SL, Barast L, Débarre D, Bouchiat H, Friend RH, Chepelianskii AD. Room temperature magneto-optic effect in silicon light-emitting diodes. Nat Commun 2018; 9:398. [PMID: 29374170 PMCID: PMC5785965 DOI: 10.1038/s41467-017-02804-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 12/28/2017] [Indexed: 12/04/2022] Open
Abstract
In weakly spin-orbit coupled materials, the spin-selective nature of recombination can give rise to large magnetic-field effects, e.g. on the electro-luminescence of molecular semiconductors. Although silicon has weak spin-orbit coupling, observing spin-dependent recombination through magneto-electroluminescence is challenging: silicon's indirect band-gap causes an inefficient emission and it is difficult to separate spin-dependent phenomena from classical magneto-resistance effects. Here we overcome these challenges and measure magneto-electroluminescence in silicon light-emitting diodes fabricated via gas immersion laser doping. These devices allow us to achieve efficient emission while retaining a well-defined geometry, thus suppressing classical magnetoresistance effects to a few percent. We find that electroluminescence can be enhanced by up to 300% near room temperature in a seven Tesla magnetic field, showing that the control of the spin degree of freedom can have a strong impact on the efficiency of silicon LEDs.
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Affiliation(s)
- F Chiodi
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N-Orsay, Orsay, 91405, France
| | - S L Bayliss
- Laboratoire de Physique des solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, LPS-Orsay, Orsay, 91405, France
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 OHE, UK
| | - L Barast
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N-Orsay, Orsay, 91405, France
- Laboratoire de Physique des solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, LPS-Orsay, Orsay, 91405, France
| | - D Débarre
- Laboratoire de Physique des solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, LPS-Orsay, Orsay, 91405, France
| | - H Bouchiat
- Laboratoire de Physique des solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, LPS-Orsay, Orsay, 91405, France
| | - R H Friend
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 OHE, UK
| | - A D Chepelianskii
- Laboratoire de Physique des solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, LPS-Orsay, Orsay, 91405, France.
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Jamali S, Joshi G, Malissa H, Lupton JM, Boehme C. Monolithic OLED-Microwire Devices for Ultrastrong Magnetic Resonant Excitation. NANO LETTERS 2017; 17:4648-4653. [PMID: 28665134 DOI: 10.1021/acs.nanolett.7b01135] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Organic light-emitting diodes (OLEDs) make highly sensitive probes to test magnetic resonance phenomena under unconventional conditions since spin precession controls singlet-triplet transitions of electron-hole pairs, which in turn give rise to distinct recombination currents in conductivity. Electron paramagnetic resonance can therefore be detected in the absence of spin polarization. We exploit this characteristic to explore the exotic regime of ultrastrong light-matter coupling, where the Rabi frequency of a charge carrier spin is of the order of the transition frequency of the two-level system. To reach this domain, we have to lower the Zeeman splitting of the spin states, defined by the static magnetic field B0, and raise the strength of the oscillatory driving field of the resonance, B1. This is achieved by shrinking the OLED and bringing the source of resonant radio frequency (RF) radiation as close as possible to the organic semiconductor in a monolithic device structure, which incorporates an OLED fabricated directly on top of an RF microwire within one monolithic thin-film device structure. With an RF driving power in the milliwatt range applied to the microwire, the regime of bleaching and inversion of the magnetic resonance signal is reached due to the onset of the spin-Dicke effect. In this example of ultrastrong light-matter coupling, the individual resonant spin transitions of electron-hole pairs become indistinguishable with respect to the driving field, and superradiance of the magnetic dipole transitions sets in.
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Affiliation(s)
- Shirin Jamali
- Department of Physics and Astronomy, University of Utah , 115 S, 1400 E, Salt Lake City, Utah 84112, United States
| | - Gajadhar Joshi
- Department of Physics and Astronomy, University of Utah , 115 S, 1400 E, Salt Lake City, Utah 84112, United States
| | - Hans Malissa
- Department of Physics and Astronomy, University of Utah , 115 S, 1400 E, Salt Lake City, Utah 84112, United States
| | - John M Lupton
- Department of Physics and Astronomy, University of Utah , 115 S, 1400 E, Salt Lake City, Utah 84112, United States
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , Universitätsstrasse 31, 93040 Regensburg, Germany
| | - Christoph Boehme
- Department of Physics and Astronomy, University of Utah , 115 S, 1400 E, Salt Lake City, Utah 84112, United States
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